I'm wondering if you have any interest in this...
I've enjoyed sharp knives most of my life. Always keeping an eye out for better ways to sharpen them. I've known for years that while sharpening, it's important to maintain a single angle on the secondary bevel; don't allow the sharpener media to wobble or change the angle. What that angle is, matters according to what type blade it is, and how will it be used. The grade of steel is very important, as well as the primary bevel of the blade. Using progressively finer sharpening media, as well as the applied pressure are all factors of getting a blade sharp.
Let's start with an image showing knife part terms. The source is in the image:
So you start with a good blade, preferably high carbon steel with a hardness of around 60HRC. High performance chef's knives run up to 63HRC in hardness. A great knife needs a balance between hardness - which will take and hold a great edge but be brittle - and toughness or flexibility without breaking. Samurai swords have a much harder edge than the back of the blade - they vary the temper across the chord of the blade from spine to edge by covering the spine and flat of the blade with clay in the tempering process. They also hand forge the steel, folding over layer upon layer of steel by hammer-welding them. This is the basis of Damascus steel. True Samurai swords are incredibly crafted, can take a LOT of time and the cost is high.
I recently acquired a premium chef's knife. It's handmade by a Japanese craftsman. Damascus steel, hammer forged with 67 layers of high-carbon steel, 1 7/8" of max chord. Has great reviews online, very sharp and stays sharp longer than may be expected. Requires hand washing, no soaking, dry immediately and apply some oil. They say it's sharpened at 12° while my laser goniometer reports it is.
Here it is.
OK, so now while I have a premium chef's knife I need to get more serious on sharpening. Enter the laser goniometer. It's a device that lets you evaluate the edge or secondary bevel by reflecting a laser off it onto a degree scale. Works quite well and not really costly. You can determine what sharpening method really works, if a blade needs sharpening, and if it's sharpened correctly for purpose.
Here's the box. Available at Amazon.
I knew some time ago a precision sharpener was available, that lets you set your angle precisely. But they wanted a LOT for it; I recall around $500 or so. I said I'm not paying that.
Well last week I looked into getting a precision sharpener, and I bought one that allows angle setting. Based on the same concept as AccuSharp but with adjustable angles. It came in, and I wasn't impressed.
I'll probably keep it for sharpening cheap knives. But I need a better soln for quality cutlery. Here's what it looks like.
I checked back into the precision sharpener that was so spendy. Hey, they had a change in their business plan. Maybe their patent expired. Whatever. Now they are selling it at a reasonable price! Here's the box.
You can set the angle from 15° to 30°, it has 5 different grits of diamond stones, ceramic and a leather strop. (the setting goes down to about 12° but the graduations stop at 15°) It's very effective in creating a precision edge, in less time than you'd expect. And even reprofiling an edge to a new angle, or repair it, in short order. Now for cheap knives, I'd say don't bother. Just use an AccuSharp and in 3 swipes you have a usable knife. But for precision knife work, like butchering a deer, or creating masterpieces in vegetable & meats in the kitchen, a high quality chef's knife (or meat cutter knife) with the edge this Precision Adjust Work Sharp Elite tool produces will help you as a culinary artist. Or if you just like to take appropriate care of your quality knives, this is the ticket. IMHO.
FYI. Razors have an edge bevel of 8° (each side, not inclusive). Incredibly sharp but delicate. Don't last at all. Chef's knives typically 12-15°. Extremely sharp, need honing/steeling often. If high carbon steel, need extra care but stay sharp longer. Common kitchen cutlery, around 18°, reasonably sharp for different uses while holding their edge a bit longer. Pocket knives, 20-21°. Can be quite sharp and last longer. Hunting knives, up to 24°. Least sharp but last the longest of knives. Then you get into utility edges like axes, hatchets and so on. Not germane to this discussion.
OK Now some examples.
This is a Santoku Chef's knife, German steel.
"Santoku translates to 'three virtues' or 'three uses,' and these uses are mincing, dicing, and slicing. Santoku knives are designed primarily for precision work: cutting thin slices. You can use them for chopping cheese, herbs, fish, and various vegetables. They are particularly suited for preparing sashimi and sushi plates. Although some Santoku knives have a double-sided blade, the original Japanese Santoku knives have a single-sided blade. This allows chefs to have more control when they’re cutting. The Granton edge is another significant feature of Santoku knives." Those are “scallops" on the side of the primary grind that releases ingredients like cucumber or fish from sticking to the knife. This knife style was invented by Japanese master chefs. I've had this knife since 2015, and have sharpened it on my belt sanders held to a 20° angle (as best I could using a magnetic angle finder) using 2 grits, then buffed on my high speed buffer with 2 grits of sharpening compound (rouge). I didn't know about the one-sided edge of original Santokus - but this one never was. Not sure this sharpener could support that, with rapid use. (Maybe two of these sharpeners, each set up for one side of the knife would work.) The scallops are only on the left side - which makes me think this is a left-handed knife - I need the scallops on the right.
(Quote from
https://seidoknives.com/blogs/news/santoku-vs-chef-knife)
Now on the laser goniometer, when aligned properly on the edge, you will see two laser reflections near the zero - these are off the flats of the blade - not important. The laser spots further out on the scale are reflected off the secondary bevels of the edge. If dull you will see smears of light. If sharp, they will be bright spots and located at the angle you ground on the bevels. Here's my Santoku on the goniometer, as it sat on my butcher block - usable for some use in the kitchen, as it would tear it's way through food. Note there are no spots out on the scale but smears.
OK now sharpening the Santoku on the Precision Adjust Elite. I designated it at 15°. BTW all the other knives in the pic are Gerber, Schrade, Knives of Alaska (D2 steel), or Victorinox - all US or Swiss made. As with all sharpening, you grind one side until a burr appears on the opposite side. They say to feel it - but I found I can SEE it sooner with a bright light - hence the flashlight. On the actual technique of sharpening with this tool: They cover that well in the instructions so I won't detail it here. I'll add if it's the first sharpening of a given knife and it's really dull and/or you want to establish a different angle profile, then you start with the coarsest grit and use many more strokes than they suggest. If re-sharpening when the edge bevel is established you start closer to the final grits. The point is, monitor the appearance of a burr on the opposite side & once it appears, you can stop and turn the blade to the other side. As they say, count the strokes so you repeat on the other side. Of course you progress from course to fine grit, generally reducing the stroke count and the pressure through the process. Done properly this tool provides factory sharpness or better.
Now the Santoku on the goniometer. I got 13.5°. It's not aligned perfectly - shift it to the right. These pics took 2 people, 2 hands on the tool & knife & 2 on the camera, alignment & focus.
I sharpened the SwissTool multi-tool, set for 19°. Because the heel or chord of the blade is too narrow for the clamp to clear the grinding media, I opened the adjacent tool which is the file, clamped on that, which effectively gave me large enough chord for the clamp to clear while grinding a narrow angle. Like this:
The result on the goniometer:
Here's the Seido chef's knife as it came, in the box. Unused and unsharpened. 12°.
All of these knives slice through paper like a razor, and of course shave the hair off your arm. The Precision Adjust Elite sharpener was $126.23 delivered from Amazon. The goniometer Laser Knife Edge Reader was $34.88 delivered. Both tools work as well or better than they claim.
Some caveats I found:
- The sharpener requires enough "heel" between the spine and edge so the blade clamp will clear the grinding media - especially as the grind angle becomes narrower. This means some knives can't be clamped in it. Like filet knives, or pocket knives with small heel measurements.
- You need enough width of the "flat" for the clamp to hold onto a good part of it. If the "swedge" reduces the width of the flat too much, it will have trouble holding the blade still while you move the grinding media between the tip and the choil along the edge.
- This sharpener doesn't really sharpen serrated knives - though they say they do. OK I didn't try using their tiny ceramic rod for that, so I could be FOS. They incorporated that into the back of their leather hone tool. It's only an inch long so I have doubts on it.
